Abstract

The use of GaAsSbN capping layers on InAs/GaAs quantum dots (QDs) has recently been
proposed for micro- and optoelectronic applications for their ability to independently
tailor electron and hole confinement potentials. However, there is a lack of knowledge
about the structural and compositional changes associated with the process of simultaneous
Sb and N incorporation. In the present work, we have characterized using transmission
electron microscopy techniques the effects of adding N in the GaAsSb/InAs/GaAs QD
system. Firstly, strain maps of the regions away from the InAs QDs had revealed a
huge reduction of the strain fields with the N incorporation but a higher inhomogeneity,
which points to a composition modulation enhancement with the presence of Sb-rich
and Sb-poor regions in the range of a few nanometers. On the other hand, the average
strain in the QDs and surroundings is also similar in both cases. It could be explained
by the accumulation of Sb above the QDs, compensating the tensile strain induced by
the N incorporation together with an In-Ga intermixing inhibition. Indeed, compositional
maps of column resolution from aberration-corrected Z-contrast images confirmed that
the addition of N enhances the preferential deposition of Sb above the InAs QD, giving
rise to an undulation of the growth front. As an outcome, the strong redshift in the
photoluminescence spectrum of the GaAsSbN sample cannot be attributed only to the
N-related reduction of the conduction band offset but also to an enhancement of the
effect of Sb on the QD band structure.